Myelination is a complex developmental process seen only in the nervous system, whereby a specialized glial membrane, the myelin sheath, is elaborated around axons. In mice there are a number of neurological mutants whose phenotypic expression is abnormal myelination. One of those mutants, the shiverer mouse, has been shown to have a partial deletion of the myelin basic protein (MBP) gene. This single gene codes for four different forms of MBP, a major myelin protein. The first objective of this proposal is to identify in vitro those cis-acting regulatory elements responsible for the expression of MBP in the oligodendrocyte. A second objective is to utilize methods for the production of transgenic systems to transfer the cloned MBP gene into the genetic background found in the shiverer mouse. A genomic clone containing the entire genomic structure of the MBP gene and a cDNA clone for the 18.5kd form of MBP will be expressed in transgenic animals using the flanking regions of the MBP gene. These transgenic systems will be used for the following purposes: (1) to identify those cis elements involved in the high level expression of the myelin basic proteins in the oligodendrocyte; (2) to examine which tissues and cell types possess the trans factors necessary for utilization of these cis elements; (3) to analyze the splicing patterns that are responsible for the different forms of MBP; and (4) to study whether multiple forms of MBP are necessary for myelination, by expressing only one form of MBP in a transgenic shiverer mouse. The objective of this study is to utilize molecular biology and genetic mutations affecting myelination to advance the understanding of the biology of myelination. This understanding will be crucial to the future determination of how this biology is altered in the dysmyelinating and demyelinating disorders of man.